Spiral blade stabilizer



3, 1966 J. E. ORTLOFF ET AL 3,2682% SPIRAL BLADE STABILIZER 2Sheets-Sheet Filed May 25, 1964 William D. Smiley John E. Orlloff INVENTOR S BY %.w-. E. Q;

ATTORNEY Aug. 23, 1966 J. E. ORTLOF'F ET AL 3,2682% SPIRAL BLADESTABILIZ-ER 2 Sheets-Sheet 2 Filed May 25, 1964 FIG. 4

FIG. 3

William D. Smiley John E. Orf/off INVENTORS BY E. Q;

ATTORNEY United States Patent 3,268,274 SPIRAL BLADE STABILIZER John E.Ortloif and William D. Smiley, Tulsa, Okla,

assignors, by mesne assignments, to Esso Production Research Company,Houston, Tex., a corporation of Delaware Filed May 25, 1964, Ser. No.369,735 7 Claims. (Cl. 308-4) The present invention relates to rotarydrilling equipment and is particularly concerned with improved drillstring stabilizers useful in drilling oil wells, gas wells and similarboreholes.

Stabilizers are widely used to center the drill string in the holeduring oil field rotary drilling operations. The typical stabilizeremployed for this purpose consists of a tubular sub fitted with rigidexternal ribs which bear against the borehole wall as the drill stringrotates. Because of abrasion which occurs when the ribs move in contactwith the wall, tungsten carbide or a similar refractory material isgenerally applied to the outermost rib surfaces by means of an electricare or oxyacetylene torch. This improves stabilizer life but is notwholly satisfactory. Experience has shown that materials thus appliedgenerally have rough outer surfaces which may cause excessive wear ofthe casing and other equipment in the borehole, that they often containflaws due to slag or gas inclusions and are usually highly stressedbecause of differences in thermal expansion, and that such materials aregenerally softened or degraded as they are welded in place. In addition,the large rough particles of tungsten carbide applied by the weldingprocess protrude from the weld metal and break relatively easily underimpact as the blades contact the borehole wall. As a result of these andrelated difficulties, conventional stabilizers wear undersize quicklyand generally have to be rebuilt at frequent intervals to maintain theireffectiveness.

The present invention provides a new and improved stabilizer whicheliminates many of the difiiculties encountered with stabilizersavailable in the past. The stabilizer of the invention is characterizedby spiral segmented ribs which extend longitudinally over the majorportion of the tool surface. Each rib segment is hardfaced on its outersurface with closely spaced blocks of tungsten carbide, with spheroidalgranules of tungsten carbide or with a similar material set in asuitable matrix. It has been found that such stabilizers can readily befabricated with smooth outer surfaces which will not severely damage thecasing or other equipment in the bore hole, that the segmented ribs aresurprisingly resistant to wear and abrasion, and that such stabilizersgenerally have a useful life at least three times that of theconventional tool.

The nature and objects of the invention can best be understood byreferring to the following detailed description of the improvedstabilizer and to the accompanying drawing, in which:

FIGURE 1 is a vertical elevation, partially in section, of oneembodiment of the stabilizer which includes segmented ribs bondeddirectly to the tool body;

FIGURE 2 is an enlarged cross-section through a rib segment taken alongthe line 22 in FIGURE 1;

FIGURE 3 is a vertical elevation, partially in section, of an alternateembodiment of the invention in which the rib segments are formed onsleeves attached to the tool body; and

FIGURE 4 is a cross-sectional view through the stabilizer of FIGURE 3taken about the line 44.

The stabilizer shown in FIGURE 1 of the drawing includes an elongatedtubular body 11 provided with an 3,268,274 Patented August 23, 1966A.P.I. tool joint box at its upper end and with an A.P.1. tool joint pin12 at its lower end. These permit connection of the tool at anintermediate position in a conven tional rotary drill string. Otherconnecting means may be utilized in lieu of the box and pin if desired.An internal passageway, not shown in the drawing, extends through thebody to permit the circulation of drilling fluid. Spiral ribs 15, 16 and17 are mounted on the outer surface of body 11 and are spaced atintervals of about the body periphery. As indicated by referencenumerals 15a, 15b and 15c, each rib is made up of three longitudinalsegments which are separated from one another to form a discontinuousspiral extending about the body through an angle of about 120. This useof segmented ribs minimizes difficulties encountered due to differencesin the coefficients of thermal expansion of the rib metal and hardfacingmaterial, limits the adverse effect of failure of the carbide at aparticular point, reduces abrasion caused by the entrapment of particlesbetween the rib surface and the borehole wall, and permits fabricationof the tool in sizes which would not otherwise be feasible.

The rib structure is shown more clearly in FIGURE 2 of the drawing. Asshown in FIGURE 2, each rib includes a supporting member 18 of steel,aluminum or similar metal containing a channel in its outer surface.This channel is filled with a matrix 19 formed of closely spaced powdergranules of tungsten carbide or a similar refractory hard metal carbidebonded together with a metallic binder. Suitable binders include castiron, iron nickel alloys, copper-nickel alloys, copper-nickel-tinalloys, copper-nickel-manganese alloys, iron-nickel-manganese alloys,S-Monel and other alloys having melting points in the range betweenabout 1500 F. and about 2500 F. and the ability in the molten state towet the refractory hard metal carbide granules employed. Cubes,cylinders or similar pieces 20 of tungsten carbide, titanium carbide,tantalum carbide, tungsten carbide-titanium carbide, or a similarrefractory hard metal carbide are embedded in the matrix in a regularpattern so that each piece presents a smooth outer face. The use ofcemented tungsten carbide containing from about 3 to about 15% cobalt asthe cementing agent is preferred. The cubes or other carbide bodies willnormally be between about one-eighth and about one-half inch in size andshould be spaced from' about one-sixteenth to about one-fourth inchapart. This permits the concentration of a large quantity of carbide atthe outer surface of the rib and yet avoids difiiculties encounteredwhen a continuous or substantially continu-' ous facing of carbide isused. The matrix between the carbide bodies is sufficiently ductile toresist fracturing under high impact loading and is hard and erosionresistant because of the carbide powder granules contained therein. Thepowder granules also increase the strength of the matrix so that thereis little chance of dislodging the carbide cubes or similar bodies eventhough a Wide spacing is used. The hardfacing material may extend ashort distance above the surface of the surrounding rib body if desiredbut this is not essential.

The ribs employed on the stabilizer of the invention may be fabricatedby first preparing a carbon or ceramic mold containing a cavity shapedto receive a rib segment. The mold should be designed so that thechannel in the outer surface of the rib body can be placed adjacent asurface to which the carbide cubes or similar bodies can be glued orotherwise affixed and should be provided with a port through which thebinder metal can be introduced. Cubes, cylinders or other bodies oftungsten carbide, tantalum carbide, titanium carbide, molybdenumcarbide, tungsten carbide-titanium carbide or a similar refractory hardmetal carbide having smooth outer faces are mounted on this surface inthe desired pattern. The rib body is then placed in the mold so that thecubes or other bodies extend into the channel. The space surrounding thecubes is packed with powdered tungsten carbide or the like between about100 mesh and about 400 mesh in size. The powder utilized may be eitherangular powder prepared by crushing pieces of cast, tungsten carbide orspheroidal powder obtained by melting tungsten carbide and cooling theresultant droplets in a gas stream. The mold may be vibrated and pressedat moderate pressures to compact the powder and reduce porosity ifdesired.

After the mold has thus been prepared, it is placed in a furnace andheated to a predetermined infiltration temperat-ure in the range betweenabout 2000 F. and about 2600 F. The temperature selected will dependprimarily upon the melting point and infiltration characteristics of thebinder metal utilized. Temperatures at least 100 F. above the meltingpoint of the binder are generally necessary. After the mold has reachedthe infiltration temperature, a molten binder alloy previously heated tothe same temperature is introduced through the port and allowed toinfiltrate into the interstices between the carbide bodies, powdergranules, and rib body. The molten binder wets and alloys with thecarbide and steel. The mold is held at the infiltration temperature fora period of from about 3 minutes to about minutes or longer and is thenremoved from the furnace and allowed to cool. It is preferred that themold be cooled rapidly until a temperature below the melting point ofthe binder alloy is reached and that thereafter it be cooled slowly toroom temperature in order to avoid adversely affecting the grainstructure of the steel. After the rib has reached room temperature, itmay be removed from the mold and machined or sand blasted to remove anyexcess binder metal.

The rib segments thus prepared are welded in place as shown in FIGURES 1and 2 of the drawing. This may be done by first tack welding thesegments in the proper position and running narrow beads on each piece.The stabilizer body is then heated to a temperature of about 500 F. andfillet welds are built up to the desired size. It is generally advisableto alternate between pieces to prevent excessive build up of heat. Afterthe welds have been completed, the stabilizers should be slowly cooledto room temperature. It will be understood that the above procedures maybe varied somewhat depending upon the particular materials from whichthe stabilizer body and ribs are made but that a procedure similar tothat outlined will generally be followed.

In lieu of bonding the hard surfacing material to the body of the ribsegment as described above, a pad containing the tungsten carbide cubesor similar bodies, the carbide powder granules, and the binder metal maybe produced by infiltration and thereafter bonded to the outer surfaceof the rib body by a welding or brazing technique. This latter method isadvantageous under certain conditions but has disadvantages in that aless satisfactory bond is generally secured. It is therefore preferredto form the hardfacing material in contact with the rib as describedpreviously.

If spheroidal tungsten carbide powder is utilized in place of angularpowder in fabricating the ribs, the cubes or similar particles oftungsten carbide or the like may be omitted. Tests have shown thatspheroidal powder granules properly prepared are harder thancorresponding angular granules and that the use of spheroidal granulesbetween about 100 and about 400 mesh on the Tyler screen scale permitsthe formation of rib surfaces which are smooth and highly resistant toabrasion and impact. The fabrication methods employed with thespheroidal powder are similar to those used with the angular powder andcubes or other particles.

FIGURES'S and 4 of the drawing depict an alternate embodiment of theinvention in which the stabilizer ribs are formed on sleeves mounted onthe body. This embodiment is similar to that described earlier in thatit includes an elongated tubular body 30 provided with an A.P.I. box atits upper end and an A.P.I. pin 31 at its lower end. An internalpassageway permits the circulation of drilling fluid through theapparatus. Sleeves 34, 35 and 36 are mounted on the outer surface of thebody and are welded or brazed in place as shown. The sleeves extendlongitudinally over only part of the body so that sufiicient space isleft near the box and pin to permit engagement of the tool with thetongs normally used in rotary drilling operations. Each sleeve contains3 integral ribs spaced at 120 intervals about the tool periphery. Theseribs are indicated on sleeve 34 by reference numeral-s 37, 38 and 39.The rib segments on the sleeve are aligned to form discontinuous ribswhich extend about the body through angles of about 120. This use ofintegral sleeves and ribs as shown simplifies fabrication of the tooland facilitates the making up of stabilizers of various lengths. Theintegral rib segments of the apparatus shown in FIGURES 3 and 4 of thedrawing are hardfaced with a material similar to that described earlier.Cubes or similar particles 40 of cemented tungsten carbide or the likemay be embedded in a surrounding matrix composed of cast tungstencarbide powder and a binder alloy or, alternately, the material mayconsist of spheroidal tungsten carbide granules bonded together with abinder alloy.

The hardfacing material, ribs and supporting sleeve are fabricated as aunit in a graphite mold machined to the desired shape. Cubes or similarsintered carbide bodies may be glued to the mold surfaces correspondingto the outer rib faces. Tungsten carbide powder between about and about400 Tyler mesh size, either angular or spheroidal, can then be packedinto the rib cavities about the cubes. A small amount of wax or otherorganic binder may be added to the powder to assist in holding it inplace if desired. After the mold and its contents have been heated tothe infiltration temperature in a furnace, a molten iron nickel alloycontaining about 10% nickel or a similar binder metal previously heatedto the infiltration temperature is permitted to flow into the annularspace in the mold and infiltrate into the interstices between thecarbide powder granules and cubes. The mold is then removed from thefurnace and allowed to cool. The exposure of the cubes to the moltenbinder should be limited to 30 minutes or less, preferably less thanabout 15 minutes, so that the original hardness of the carbide is notlost. The finished casting thus consists of a sleeve of the binder metalhaving integral ribs with carbide cubes surrounded by tungsten carbidegranules at the outer rib surfaces. This casting is then slipped overthe stabilizer body and welded in place. If desired, two sleeves can beWelded in place, one at either end of the tool body rather than three atthe center of the body as shown leaving space for the tongs between twoadjacent sleeves. In some cases it may also be desirable to secure thesleeves on the body by means of collars held in place at either end sothat the sleeves themselves are free to rotate with respect to the body.This reduces relative motion between the rib surfaces and the boreholewall and may thus further extend stabilizer life. These and othermodifications will be readily apparent to those skilled in the art.

The advantages of the stabilizers of the invention over conventionaltools are shown by the results of comparative tests carried out duringan extended oil field drilling program. Tests of conventionalstabilizers hard-faced with tungsten carbide applied by means of awelding torch showed that such stabilizers normally were severely wornafter only a few thousand feet and had to be rebuilt after each well.Tests with a stabilizer of the type shown in FIGURES 1 and 2 of thedrawing were then carried out in the same area under comparableconditions. This stabilizer was used in three different wells. The totaldepth was about three times that drilled with the conventionalstabilizers. Upon completion of the third well, it was found that thestabilizer ribs showed essenially 19 gns Of wear. The gage diameterswere essentially unchanged. There was no evidence of fracturing orfailure of the hard surfacing material on the rib surfaces. Nodifiiculties due to excessive wear of the surface casing wereencountered. This improved performance significantly reduces the cost ofusing stabilizers to control borehole deviation.

What is claimed is:

1. A drill string stabilizer which comprises:

(a) a tubular body member provided with means near the upper and lowerends thereof for connecting said body member at an intermediate positionin a rotary drill string;

(b) a plurality of spiral ribs extending outwardly beyond said bodymember at spaced intervals about the periphery thereof, said ribs beingmade up of longitudinal segments arranged in spaced end-to-endrelationship; and,

(c) a hardfacing material bonded to said rib segments to form smoothouter surfaces, said hardfacing material comprising refractory hardmetalcarbide powder granules between about 100 and about 400 mesh on theTyler screen scale bonded together with a metallic binder having amelting point between about 1500 F. and about 2500 F. and in the moltenstate having the ability to wet said powder granules.

2. A stabilizer as defined by claim 1 wherein said powder granules arespheroidal granules of tungsten carbide.

3. A stabilizer as defined by claim 1 wherein said rib segments aremounted on sleeves which are in turn mounted on said body member.

4. A drill string stabilizer which comprises:

(a) a tubular body member provided with means near the upper and lowerends thereof for connecting said body member at an intermediate positionin a rotary drill string;

(b) a plurality of elongated rib segments bonded in place on the outersurface of said body member to form spiral ribs extending part wayaround said body member at spaced intervals about the periphery thereof,each of said ribs being composed of at least two segments mounted inspaced end-to-end relationship; and,

'(c) a hardfacing material bonded to the outer faces of said ribsegments to form smooth outer surfaces, said hardfacing materialcomprising a plurality of preformed bodies of cemented hardmetal carbidehaving smooth outer faces between about inch and about inch in sizespaced from about to about 4 inch apart in a regular pattern, refractoryhardmetal carbide powder granules between about 100 and about 400 Tylermesh between said preformed bodies, and a metallic binder having amelting point between about 1500 F. and about 2500 F. and the ability towet said preformed bodies and powder granules in the molten statebonding said bodies and granules together.

5. A drill string stabilizer which comprises:

(a) a tubular body member provided with means near the upper and lowerends thereof for connecting said body member at an intermediate point ina rotary drill string;

(b) a plurality of sleeves mounted on said body member at verticallyspaced intervals, said sleeves having external rib segments on the outersurfaces thereof and said rib segments on adjacent sleeves being alignedto form discontinuous spiral ribs; and,

(c) a hardfacing material bonded to said rib segments to form smoothouter surfaces, said hardfacing material comprising refractory hardmetalpowder granules between about and about 400 mesh on the Tyler screenscale bonded together with a metallic binder having a melting pointbetween about 1500 F. and about 2500 F. and in the molten state havingthe ability to wet said powder granules.

6. A drill string stabilizer which comprises:

(a) a tubular body member provided with means near the upper and lowerends thereof for connecting said body member at an intermediate positionin a rotary drill string;

(b) a plurality of rib segments welded to the outer surface of said bodymember to form discontinuous spiral ribs located at intervals of aboutabout the periphery of said body member and extending through angles ofabout 120; and,

(c) a hardfacing material bonded to the outer faces of said rib segmentsto form smooth outer surfaces, said .hardfacing material comprisingspheroidal tungsten carbide granules between about 100 and about 400mesh on the Tyler screen scale bonded together with a copper-nickelalloy having a melting point between about 1500 F. and about 2500 F. andin the molten state having the ability to wet said powder granules.

7. A stabilizer as defined by claim 6 wherein said hardfacing materialincludes cubes of cobalt-cemented tungsten carbide between about A; andabout /2 inch in size.

References Cited by the Examiner UNITED STATES PATENTS 2,248,530 8/1941Granger 308241 2,657,907 ll/1953 Cochran l66241 2,667,930 2/ 1954Saurenmon l66173 3,054,647 9/ 1962 Rosenberg 308-4 DAVID J.WILLIAMOWSKY, Primary Examiner. L. L. JOHNSON, Assistant Examiner.

1. A DRILL STRING STABILIZER WHICH COMPRISES: (A) A TUBULAR BODY MEMBERPROVIDED WITH MEANS NEAR THE UPPER AND LOWER ENDS THEREOF FOR CONNECTINGSAID BODY MEMBER AT AN INTERMEDIATE POSITION IN A ROTARY DRILL STRING;(B) A PLURALITY OF SPIRAL RIBS EXTENDING OUTWARDLY BEYOND SAID BODYMEMBER AT SPACED INTERVALS ABOUT THE PERIPHERY THEREOF, SAID RIBS BEINGMADE UP OF LONGITUDINAL SEGMENTS ARRANGED IN SPACED END-TO-ENDRELATIONSHIP; AND (C) A HARDFACING MATERIAL BONDED TO SAID RIB SEGMENTSTO FORM SMOOTH OUTER SURFACES, SAID HARDFACING MATERIAL COMPRISINGREFRACTORY HARDMETAL CARBIDE POWDER GRANULES BETWEEN ABOUT 100 AND ABOUT400 MESH ON THE TYLER SCREEN SCALE BONDED TOGETHER WITH A METALLICBINDER HAVING A MELTING POINT BETWEEN ABOUT 1500*F. AND ABOUT 2500*F.AND IN THE MOLTEN STATE HAVING THE ABILITY TO WET SAID POWDER GRANULES.